1. Field of the Invention
The present invention is directed to the movement of drilled cuttings (wet, damp, or dry), to the positive pressure pneumatic transport of such drilled cuttings solids, and, in particular aspects, to the movement of oilfield drilled cuttings or other solids for disposal, onward transportation, storage or further processing.
2. Description of Related Art
The prior art discloses various methods for the positive pressure pneumatic continuous pneumatic transport of low slurry density and low particle density dry solids and non-continuous high slurry density transport of high particle density wet material. Many low density slurries typically have particles mixed with air with a specific gravity less than 1.0. The prior art discloses various methods that employ the vacuum transport of high particle and low particle density solids.
To drill an oil or gas well, a drill bit at the end of a drill string is rotated to drill the borehole in the earth. A drilling fluid (“drilling mud”) pumped through the drill string to the drill bit lubricates the drill bit and carries drilled cuttings produced and other solids and debris to the surface through an annulus between the drill string's exterior and the borehole's interior. Due to its expense, attempts are made to recover and re-use the used drilling mud. Solids are removed from the drilling mud by, e.g. vibratory separators, such as those shale shakers disclosed in U.S. Pat. No. 5,265,730, WO 96/33792 and WO 98/16328. Recovered drilling mud is received in a reservoir or receptacle beneath a shale shaker and separated solids (e.g. drilled cuttings) move off the top of the shaker's screens into a ditch, receptacle, or skip.
Drilled cuttings having processed by a shale shaker can contain approximately 10% to 20% moisture (oil, water) by weight.
It is now often desirable and/or legislatively required to transport recovered drilled cuttings to a processing site on shore to remove substantially all of the oil and contaminates therein so that the drilled cuttings can be disposed of or used in an environmentally safe and friendly way. Environmental agencies around the world are moving towards a “zero discharge” policy from offshore rigs. Continuous drilling on an offshore oil rig is common and drilled cuttings are stored on the rigs until they can be transported by ships known as supply boats which collect the oily drill cuttings and take them to another site for further processing. There is a need to efficiently and effectively store the oily drilled cuttings on the rig and also a need to efficiently and effectively store the cuttings on supply boats.
In certain prior art systems oily drill cuttings are loaded into vessels, skips or cuttings boxes which are lifted by a crane onto a supply boat.
U.S. Pat. No. 6,702,539 issued Mar. 9, 2004, PCT publication number WO 00/76889 and European Patent No. EP 1,187,783 B1 disclose systems for transporting drill cuttings in the form of a non-free flowing paste, the system comprising a pressure vessel having a conical hopper discharge portion having a cone angle sufficient to induce mass flow. The drill cuttings are stored on a rig and supply boat in ISO sized storage vessels which have a conical hopper discharge portion, such that the ISO sized container vessels can be discharged between each other on the rig and ship and between the ship and port.
German Patent No. DE 40 10 676 discloses an apparatus for conveying sewage sludge or concrete. The apparatus comprises a pressure vessel having a feed opening and a screw conveyor therebelow. Paddles act as a stirrer and forcibly fill the screw conveyor through an opening in the pressure vessel. The sewage sludge or concrete is moved by the screw conveyor into a nozzle into which compressed air is applied to move the sewage sludge or concrete along a pipe in a continuous stream.
United Kingdom Patent No. GB-A-2,330,600 discloses a system for transporting oil drill cuttings from a rig to shore. The system comprises the steps of mixing the oily drill cuttings with a mud to form a slurry, storing the slurry in retention tanks on the rig and subsequently pumping the slurry to retention tanks on a ship for transportation to shore.
There has long been a need, recognized by the present inventors, for continuous positive pressure pneumatic transport of low slurry density, high particle density material, and in certain aspects, oilfield drilled cuttings (wet, damp, or dry) or other oily/wet waste material. There has long been a need, recognized by the present inventors, for such systems which occupy relatively little space.